Feature

Toxins in the home

A guide to the potential toxins in your everyday life

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It seems that every other week, there's news of nasty toxic chemicals in the everyday items that you have round the home. Some of it is hype; some of it is rumour. But not all of it.

Short of re-qualifying as an environmental chemist, how is a parent to know how dangerous the world is for their child?

Here are a few of the myths and facts about toxins around the home.

Heavy metals

We're not talking about Metallica here. Heavy metals do occur naturally but can be concentrated in our man-made world.

With prolonged high-level exposure, they can build up in the body, with potentially dangerous effects.

In the body, metals such as lead and mercury attach to pairs of sulphur atoms in proteins and distort the shape of the protein molecule. This misshapen protein can no longer perform the bodily functions for which it was designed. This is a problem because our body's metabolism depends entirely on enzymes, which are all various types of proteins.

The operation of the brain and memory is also reliant on specific proteins. Ultimately these metals can cause brain damage to adults, but it is growing children who are most at risk.

Common heavy metals

Mercury
Fish is often cited as a source of heavy metals. Now, as a food, fish is good for you: it's high in protein, has beneficial oils and lots of trace nutrients. And while all fish contain some mercury, the levels are generally very low.

However, in large, long-living fish (particularly ones that eat lots of other fish) the mercury levels rise during their lifetime. Such fish include swordfish, broadbill and marlin, shark (flake), tuna and catfish.

Some of these fish should be avoided anyway because their populations are under threat from over-fishing, but even the plentiful species should be eaten in moderation.

The US Food and Drug Administration recommends pregnant women eat these kinds of fish no more than once a month. High levels of mercury can cause nerve damage in adults and impair nerve development in children and babies.

Lead
We thought that lead paint was a thing of the past and we only had to watch out for peeling paint in old houses.

But the recall of half a million toys from China because of lead in their paint has dispelled that complacency.

Lead, like mercury, causes damage to the brain and nerves. But how do you know if your child's toys are decorated with lead paint?

Fortunately, household lead testing kits are available from hardware stores.

Some are quite sophisticated, sensitive (detects one microgram on a solid surface) and expensive (about $30). The kit has detailed instructions on how to cut and prepare the surface for testing.

Only a few tests can be carried out with one kit as you mix the supplied substances together, applying all of it immediately.

Aluminium
Long suspected as a cause of Alzheimer's dementia, it now it appears that the characteristic aluminium deposits in the plaques in the brain are a result, not a cause, of this disease.

At any rate, aluminium cookware is less common these days. Such cookware is easily corroded and pitted.

Food acids, salt and traces of dissolved copper from domestic plumbing destroy the very thin natural protective oxide layer that spontaneously forms, then covers and protects aluminium metal from corrosion.

This layer can be deepened by a process called anodising, but is still vulnerable if acidic foods are kept in it for too long.

There are other sources of aluminium in our diet. It is present in a number of legal food additives (173, 470, 541, 555, 556, 559), but unless intake is really excessive, aluminium is not a problem.

Others
Other heavy metals, for example cadmium and chromium, are still found at low levels in pigmented plastic building blocks and toys. Cadmium causes irreversible kidney damage.